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Sep 23, 2013
09/13

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A. Patrascioiu; E. Seiler

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We comment on the recent paper by Alles et al (hep-lat/9608002)

Source: http://arxiv.org/abs/hep-lat/9608138v1

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Jul 20, 2013
07/13

by
M. Aguado; E. Seiler

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Several years ago it was found that perturbation theory for two-dimensional O(N) models depends on boundary conditions even after the infinite volume limit has been taken termwise, provided $N>2$. There ensued a discussion whether the boundary conditions introduced to show this phenomenon were somehow anomalous and there was a class of `reasonable' boundary conditions not suffering from this ambiguity. Here we present the results of some computations that may be interpreted as giving some...

Source: http://arxiv.org/abs/hep-lat/0406041v2

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Sep 18, 2013
09/13

by
A. Patrascioiu; E. Seiler

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The percolation properties of equatorial strips of the two dimensional O(3) nonlinear $\sigma$ model are investigated numerically. Convincing evidence is found that a sufficently narrow strip does not percolate at arbitrarily low temperatures. Rigorous arguments are used to show that this result implies both the presence of a massless phase at low temperature and lack of asymptotic freedom in the massive continuum limit. A heuristic estimate of the transition temperature is given which is...

Source: http://arxiv.org/abs/hep-th/0002153v1

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Sep 20, 2013
09/13

by
A. Patrascioiou; E. Seiler

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In gauge theories with continuous groups there exist classical solutions whose energy vanishes in the thermodynamic limit (in any dimension). The existence of these super-instantons is intimately related to the fact that even at short distances perturbation theory can fail to produce unique results. This problem arises only in non-Abelian models and only starting at O(1/beta^2).

Source: http://arxiv.org/abs/hep-lat/9402003v1

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Sep 22, 2013
09/13

by
A. Patrascioiu; E. Seiler

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We comment on the recent paper by Balog and Niedermaier [hep-th/9701156].

Source: http://arxiv.org/abs/hep-th/9707010v1

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Sep 21, 2013
09/13

by
A. Patrascioiu; E. Seiler

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In dimension $D\leq 2$ the low temperature behavior of systems enjoying a continuous symmetry is dominated by super-instantons: classical configurations of arbitrarily low energy. Perturbation theory in the background of a super-instanton produces thermodynamic answers for the invariant Green's functions that differ from the standard ones, but only in non-Abelian models and only starting at $O(1/\beta^2)$. This effect modifies the $\beta$-function of the $O(N)$ models and persists in the large...

Source: http://arxiv.org/abs/hep-lat/9311019v1

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Sep 18, 2013
09/13

by
A. Patrascioiu; E. Seiler

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It is shown that perturbation theory in $2D$ nonlinear $\sigma$-models as well gauge theories in dimension $D\geq 2$ produces answers that depend on boundary conditions even after the infinite volume limit has been taken. This unphysical phenomenon occurs only in the non-Abelian versions of those models, starting at $O(1/\beta^2)$. It is not present in the true (nonperturbatively defined) models and represents a failure of the perturbative method. It is related to a hitherto unnoticed type of...

Source: http://arxiv.org/abs/hep-lat/9412077v1

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Sep 21, 2013
09/13

by
A. Patrascioiu; E. Seiler

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There is a growing body of evidence that the running of $\alpha_s$ predicted by perturbation (PT) theory is not correctly describing the accelerator experiments at the highest energies. A natural explanation is provided by the authors' 1992 proposal that in fact the true running predicted by the nonperturbatively defined lattice QCD is different, leading to an ultraviolet fixed point near $\alpha_s=.1$. It is explained how this can be understood from the fact that the conventional perturbative...

Source: http://arxiv.org/abs/hep-ph/9609292v1

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Jul 20, 2013
07/13

by
A. Patrascioiu; E. Seiler

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We point out that the $1/N$ expansion, which is widely invoked to infer properties of the $2D$ $O(N)$ models, is nonuniform in the temperature, i.e. with decreasing temperature the $1/N$ expansion truncated at a fixed order deviates more and more from the true answer. This fact precludes the use of the expansion to deduce low temperature properties such as asymptotic scaling for those models. By contrast, in the $1D$ $O(N)$ chains, there are no signs of such a nonuniformity.

Source: http://arxiv.org/abs/hep-lat/9407003v1

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Sep 18, 2013
09/13

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A. Patrascioiu; E. Seiler

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We study the universality between a discrete spin model with icosahedral symmetry and the O(3) model in two dimensions. For this purpose we study numerically the renormalized two-point functions of the spin field and the four point coupling constant. We find that those quantities seem to have the same continuum limits in the two models. This has far reaching consequences, because the icosahedron model is not asymptotically free in the sense that the coupling constant proposed by L"uscher,...

Source: http://arxiv.org/abs/hep-lat/0008024v2

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Jul 20, 2013
07/13

by
A. Patrascioiu; E. Seiler

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This reply tries to rectify some misunderstandings that are in our opinion contained in the Comment by Campostrini and Rossi, on our paper .

Source: http://arxiv.org/abs/hep-lat/9407030v1

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Sep 20, 2013
09/13

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M. Niedermaier; E. Seiler

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We investigate classical spin systems in $d\geq 1$ dimensions whose transfer operator commutes with the action of a nonamenable unitary representation of a symmetry group, here ${\rm SO}(1,N)$; these systems may alternatively be interpreted as systems of interacting quantum mechanical particles moving on hyperbolic spaces. In sharp contrast to the analogous situation with a compact symmetry group the following results are found and proven: (i) Spontaneous symmetry breaking already takes place...

Source: http://arxiv.org/abs/math-ph/0601049v2

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Sep 19, 2013
09/13

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A. Patrascioiu; E. Seiler

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We reply to David's comment (hep-lat/9504017) on our paper Phys.Rev.Lett. 74(1995)1920.

Source: http://arxiv.org/abs/hep-lat/9506003v1

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Sep 17, 2013
09/13

by
K. R. Ito; E. Seiler

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We point out missing links in the recent paper by Tomboulis in which he claims a rigorous proof of quark confinement in 4D lattice gauge theory. We also discuss if it is possible to correct his proof.

Source: http://arxiv.org/abs/0711.4930v1

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Sep 18, 2013
09/13

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K. R. Ito; E. Seiler

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We discuss in some detail certain gaps and open problems in the recent paper by E. T. Tomboulis, which claims to give a rigorous proof of quark confinement in 4D lattice Yang-Mills theory for all values of the bare coupling. We also discuss what would be needed to fill the gaps in his proof.

Source: http://arxiv.org/abs/0803.3019v1

Naval Postgraduate School

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Aug 20, 2011
08/11

by
Davies, Joseph E.;Seiler, Aubrey R.

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Bibliography: p. 25

Topic: Aeronautics

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Oct 7, 2015
10/15

by
Davies, Joseph E.;Seiler, Aubrey R.

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Bibliography: p. 25

Topic: Aeronautics

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Sep 20, 2013
09/13

by
A. Duncan; M. Niedermaier; E. Seiler

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We present a detailed study of quantized noncompact, nonlinear SO(1,N) sigma-models in arbitrary space-time dimensions D \geq 2, with the focus on issues of spontaneous symmetry breaking of boost and rotation elements of the symmetry group. The models are defined on a lattice both in terms of a transfer matrix and by an appropriately gauge-fixed Euclidean functional integral. The main results in all dimensions \geq 2 are: (i) On a finite lattice the systems have infinitely many nonnormalizable...

Source: http://arxiv.org/abs/hep-th/0405163v2

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Jun 29, 2018
06/18

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G. Aarts; E. Seiler; D. Sexty; I. -O. Stamatescu

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Lattice QCD at non-vanishing chemical potential is studied using the complex Langevin equation (CLE). One of the conditions for the correctness of the results of the CLE is that the zeroes of the measure coming from the fermionic determinant are outside of the distribution of the configurations, or at least in a region where support for the distribution is very much suppressed. We investigate this issue for Heavy Dense QCD (HDQCD) and full QCD at high temperatures. In HDQCD it is found that the...

Topic: High Energy Physics - Lattice

Source: http://arxiv.org/abs/1611.02931

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Jun 27, 2018
06/18

by
G. Aarts; E. Seiler; D. Sexty; I. -O. Stamatescu

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We propose two novel formulations of the hopping parameter expansion for finite density QCD using Wilson fermions, while keeping the gauge action intact. We use the complex Langevin equation to circumvent the sign problem in the theory. We perform simulations at very high order of the expansion, such that convergence is directly observable. We compare results to the full QCD results, and see agreement at sufficiently high orders. These results provide support for the use of complex Langevin...

Topics: High Energy Physics - Theory, High Energy Physics - Phenomenology, High Energy Physics - Lattice

Source: http://arxiv.org/abs/1503.08813

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Sep 18, 2013
09/13

by
R. De Pietri; A. Feo; E. Seiler; I. -O. Stamatescu

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We study the high density region of QCD within an effective model obtained in the frame of the hopping parameter expansion and choosing Polyakov type of loops as the main dynamical variables representing the fermionic matter. To get a first idea of the phase structure, the model is analyzed in strong coupling expansion and using a mean field approximation. In numerical simulations, the model still shows the so-called sign problem, a difficulty peculiar to non-zero chemical potential, but it...

Source: http://arxiv.org/abs/0705.3420v2

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Sep 23, 2013
09/13

by
R. De Pietri; A. Feo; E. Seiler; I. -O. Stamatescu

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We study the high density region of QCD within an effective model obtained in the frame of the hopping parameter expansion and choosing Polyakov-type loops as the main dynamical variables representing the fermionic matter. This model still shows the so-called sign problem, a difficulty peculiar to non-zero chemical potential, but it permits the development of algorithms which ensure a good overlap of the simulated Monte Carlo ensemble with the true one. We review the main features of the model...

Source: http://arxiv.org/abs/0710.3102v1

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Sep 22, 2013
09/13

by
J. Balog; M. Niedermaier; F. Niedermayer; A. Patrascioiu; E. Seiler; P. Weisz

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The intrinsic 4-point coupling, defined in terms of a truncated 4-point function at zero momentum, provides a well-established measure for the interaction strength of a QFT. We show that this coupling can be computed non-perturbatively and to high accuracy from the form factors of an (integrable) QFT. The technique is illustrated and tested with the Ising model, the XY-model and the O(3) nonlinear sigma-model. The results are compared to those from high precision lattice simulations.

Source: http://arxiv.org/abs/hep-th/0001097v1

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Sep 22, 2013
09/13

by
J. Balog; M. Niedermaier; F. Niedermayer; A. Patrascioiu; E. Seiler; P. Weisz

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The quantum field theory describing the massive O(2) nonlinear sigma-model is investigated through two non-perturbative constructions: The form factor bootstrap based on integrability and the lattice formulation as the XY model. The S-matrix, the spin and current two-point functions, as well as the 4-point coupling are computed and critically compared in both constructions. On the bootstrap side a new parafermionic super selection sector is found; in the lattice theory a recent prediction for...

Source: http://arxiv.org/abs/hep-lat/0106015v3

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Sep 22, 2013
09/13

by
D. Zola; F. Gomory; M. Polichetti; F. Strycek; E. Seiler; I. Husek; P. Kovac; S. Pace

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Coupling losses were studied in composite tapes containing superconducting material in the form of two separate stacks of densely packed filaments embedded in a metallic matrix of Ag or Ag alloy. This kind of sample geometry is quite favorable for studying the coupling currents and in particular the role of superconducting bridges between filaments. By using a.c. susceptibility technique, the electromagnetic losses as function of a.c. magnetic field amplitude and frequency were measured at the...

Source: http://arxiv.org/abs/cond-mat/0310158v1